GB700-88

UDC 669.14.018.29 H 40

GB National Standard of People’s Republic of China GB 700-88

Carbon Structural Steels

Issue Date: 1998-06-29

Effective Date: 1998-10-01

Issued by  National Standard Bureau

National Standards of People’s Republic of China UDC 669.14 .018.29 GB 700-88

Carbon Structural Steels

supersede: GB 700-79

This standard is prepared by reference to ISO 630 “Structural Steel” 1.

Subject and Applicable Scope

This standard specifies the technical specifications for carbon structural steels. This standard is applicable to general structural steels and engineering hot rolled steel plates and sheets, steel strips and steel bars. Such products can be used as structural steel for welding, riveting and bolting generally in delivery state. The chemical compositions specified in this standard are applicable to ingot (including continuous casting billet), steel billet and their products. 2.0 Applicable Standards

GB 222

Test Pieces Taking Method for Chemical Analysis of Steel and Tolerance for Chemical Compositions of Finished Products.

GB 223

Method for Chemical Analysis for Steel, Iron and Alloy

GB 228

Method for Metal Tensile Test

GB 232

Method for Metal Bending Test

GB 247

General Regulations for acceptance, Packaging, Marking and Quality Certificate for Steel Plates and Sheets and Steel Strips.

GB 2101 General Regulations for Acceptance, Packaging, Marking and Quality Certificate for Steel Bars GB 2106

Method for Metal Charpy (V-notch) Impact Test

GB 2975

Test Piece Taking Regulations for Mechanical and Technological Performance Tests of Steel Material

GB 4159

Method for Metal Charpy Impact Test

GB 6397

Test Pieces for Metal Tensile Test

3. Notation, Code and Symbol of Designation

3.1 Notation of Designations The designation of steel is composed of four parts in sequence: letter representing yield point, value of yield point, symbol for quality level and symbol for deoxidation method. For example: Q235-A.F 3.2 Symbol Q - the initial letter of Chinese Character for yield point; A, B, C and D: the quality levels; F - the initial letter of Chinese Character for rimed steel;  b - the initial letter of Chinese Character for se mi-killed steel;

Z - the initial letter of Chinese Character for killed steel TZ - the initial letter of Chinese Character for special-killed steel In the notation of designation, symbols “Z” and “TZ” are omitted. 4. Dimension, Shape, Weight and Allowable Deviation

The dimension, shape, weight and allowable deviation of steels shall conform to appropriate standards. 5. Technical Requirements

5.1 Designation and Chemical compositions 5.1.1 The designation and chemical compositions of steels shall conform to Table 1. Chemical composition % Designation

Grade

Si C

S

P

Mu

Deoxidation method

 Not greater than Q195

—

0.06-0.12

0.25-0.50

0.30

A Q215

0.09-0.15

B

0.045

F,b,Z

0.045

F,b,Z

0.045

F,b,Z

0.040

0.040

Z

0.035

0.035

TZ

0.045

F,b,Z

0.045

b,Z

0.050 0.25-0.55

0.30

B A

0.050

0.045 0.14-0.22 0.30-0.65

1)

0.050

1)

0.12-0.20 0.30-0.70  

Q235

0.045 0.30

C

0.18

D

0.17

0.35-0.80

A Q255

0.050 0.18-0.28

0.40-0.70

0.30

B Q275

—

0.045 0.28-0.38

0.50-0.80

0.35

0.050

 Note: 1) The upper limit of Mn content in Q235 Grade A and Grade B rimmed steel is 0.60%. 5.1.1.1 The Si content shall not be greater than 0.07% in rimmed steel; not greater than 0.17% in semi-killed steel and the lower limit of Si content in killed steel is 0.12%. 5.1.1.2

Grade D steels shall contain sufficient elements for forming fine grain crystal. For

example, the content of aluminum dissolved in acid in steel shall not be less than 0.015% or the content of pure aluminum shall not be less than 0.020%. 5.1.1.3 The residual elements, such as Cr, Ni and Cu shall not be greeter than 0.30% respectively and the N in oxygen (blown) converter steel shall not be greater than 0.008%. the analysis can be omitted provided that the supplier can make guarantee for it. As agreed by the Buyer, the Cu content in Grade A steels may be not greater than 0.35%. In this case, the supplier shall make analysis for the content of Cu, with the measured content to be recorded in quality certificate. 5.1.1.4 The residual As in steels shall not be greater than 0.080%. As for the steel made from ores containing As, the content of As shall be agreed between the buyer and the supplier. If there is no

As in the raw material, the analysis for As content may be omitted. 5.1.1.5 While guaranteeing that the mechanical properties of steel material can conform to the stipulations in this standard, The content of C and Mn in Grade A steels of all designations as well as the lower limit for the content of C and Mn in steels in other grades may be specified as delivery conditions. However, their contents (smelting analysis) shall be recorded in quality certificate. 5.1.1.6 While the supplier supplies ingot (including continuous casting billet) and billet, the supplier shall guarantee that the chemical compositions of Grade A and B steels of various designations shall conform to stipulations in Table 1. However, in order to guarantee that all  properties of rolled steel can meet the requirements in this standard, the chemical compositions of Grade A and B steels of all designations may be appropriately adjusted as required by the buyer and specified in separately agreements. 5.1.2 The allowable deviation for the chemical compositions of steel products and steel commodities shall conform to Table 1, GB222.  No guarantee will be provided for the deviation of chemical compositions of the rimmed steel  products and billet commodities. 5.2 Smelting Method The steel will be smelted in oxygen converter, open furnace or electric furnace. Unless otherwise required by the buyer and specified in contract, the smelting method shall be selected by the manufacturer. 5.3 Delivery State Steel material is delivered generally at hot-rolled (including controlled rolled) state. It may be delivered at normalized state as required by the buyer and agreed by the two parties (except for Grade A steels). 5.4 Mechanical Properties 5.4.1 the tensile test and impact test of steel shall conform to Table 2 and the bending test shall conform to Table 3.

Table 2 Tensile Test

Impact Test

Yield point N/mm 

Elongation%

!

Thickness (Dia.) of steelmm Designation

impact

Thickness (Dia.) of steelmm

Tensile

Grade

V-notch Temperature

Strength 16

>16-40

>40-60

>60-100 >100-150

>150

 N/mm

!

(longitudinal) 16

>16-40

>40-60

>60-100

>100-150

>150







Q195

Q215

Q235

— A B

(195)

(185)

—

—

—

—

315-390

33

32

—

—

—

—

215

205

195

185

175

165

335-410

31

30

29

28

27

26

—

—

 —

 —

20

27

 —

B

20

235

225

215

205

195

185

375-460

26

25

24

23

22

21

0

D

Q255

Q275

-20

A B —

255

245

235

225

215

205

410-510

24

23

22

21

20

19

275

265

255

245

235

225

490-610

20

19

18

17

16

15

direction

 — 27

—

—

Thickness (Dia.) of steel mm mm  60

>60-100

>100-200

Mandrel diameter d Q195

longitudinal

0

transverse

0.5a

longitudinal

 — 

 — 

0.5a

1.5a

2a

transverse

a

2a

2.5a

longitudinal

a

2a

2.5a

transverse

1.5a

2.5a

3a

Q255

2a

3a

3.5a

Q275

3a

4a

4.5a

Q215

Q235

 Note:  B is the width of test sample, a is the thickness (diameter) of steel 5.4.1.1

The yield point of Designation Q195 is only for information and not be taken at delivery

conditions. 5.4.1.2

27

20

Cold Bending Test B=2a 180°

Designation

 —

 —

Table 3

Test sample

J 

Not less than

A

C

energy

For tensile test and bending test, transverse test sample shall be taken for steel plates and

Table 3 Cold Bending Test B=2a 180°

Designation

Thickness (Dia.) of steel mm mm 

Test sample direction

60

>60-100

>100-200

Mandrel diameter d Q195

longitudinal

0

transverse

0.5a

longitudinal

 — 

 — 

0.5a

1.5a

2a

transverse

a

2a

2.5a

longitudinal

a

2a

2.5a

transverse

1.5a

2.5a

3a

Q255

2a

3a

3.5a

Q275

3a

4a

4.5a

Q215

Q235

 Note:  B is the width of test sample, a is the thickness (diameter) of steel 5.4.1.1

The yield point of Designation Q195 is only for information and not be taken at delivery

conditions. 5.4.1.2

For tensile test and bending test, transverse test sample shall be taken for steel plates and

sheets as well as steel strips, allowing elongation 1% (absolute value) lower than the data in Table 2; while longitudinal test sample shall be taken for profiled bars. 5.4.1.3

The cold bending test will be taken for all Grade A steels of various designations only as

required by the buyer. In case the cold bending test is acceptable, the upper limit for tensile strength may be not considered as delivery conditions. 5.4.2

Charpy (V-notch) impact test shall conform to Table 2.

5.4.2.1 Charpy (V-notch) impact energy shall be the arithmetic mean of one group of three test samples, and it is allowable for one individual value of the three test samples lower than the specified value, however, not beyond 70% lower than the specified value. 5.4.2.2 While 5mm x 10mm x 55mm small sized test sample will be used for impact test, the test results shall not be lower than 50% of the specified value. 5.4.3

In generally, the thickness (diameter) of Grade B steel of various designations rolled from

rimmed steel will not greater than 25mm. 5.5 Surface Quality The surface quality of steels shall conform to the stipulations of appropriate standards. 6. Test Method.

6.1 The inspection items, sample quantity, sampling method and testing method for each lot of steels shall conform to Table 4.  No.

Inspection Item

1

Chemical Analysis

Sample quantity 1 (for each furnace

Sampling method GB222

Testing method BG223.1-223.5 GB223.8-223.12

 No.)

GB223.18-223.19 GB223.23-223.24 GB223.31-223.32 GB223.36

2

Tensile

GB228, GB6397

3

Cold bending

GB232

4 5

Impact at room temperature Impact at low temperature

GB2106 GB4159

6.1.1 While making cold bending test for steels with thickness or diameter greater than 200mm, the test sample shall be planned at single face to reduce the thickness to 20mm and the mandrel diameter shall conform to Table 3. while testing, the non-machining surface shall be placed outside. In case the test sample is not planed, the mandrel diameter shall be the data specified in Table 3 plus a, the thickness of one test sample. 6.1.2 The longitudinal axis of impact test sample shall be paralleled to the rolling direction. 6.1.3 As for steel plates, steel sheets, steel strip, and profiled bars with thickness not smaller than 12mm and the steel bars with diameter not smaller than 16mm, 10mm x 10mm x 55mm samples shall be used for impact test; As for steel plates, steel sheets, profiled bars with thickness from 6mm to 12mm and steel bars with diameter from 12mm to 16mm, 5mm x 10mm x 55mm small sample shall be used. One rolling face can be reserved for impact test sample. 7. Inspection Regulations

7.1 The steels shall be subject to the inspection and acceptance by the technical supervision department. 7.2 The steels shall be tested and accepted by lot. Each lot shall consist of steels with same designation, same furnace No., same grad, same kind, same size and same delivery state. The weight of each lot shall not be greater than 60t. As for steel with nominal weight not greater than 30t and smelted in smelting furnace, Grade A and Grade B steels with same designation, same smelting and pouring method, different furnace  No. can be combined as one lot. However, each lot cannot contain more than 6 furnace No. and the difference of carbon content between various furnace No. shall not be greater than 0.02% and the difference of Mn content shall not be greater than 0.15% 7.3 If the Charpy (V-notch) compact test results of steels fail to meet the requirement in paragraph 5.4.2, another group of three samples shall be taken from the same lot of steels for testing, the average of the six samples shall not be lower than the specified value. However, two test samples are allowed to be lower than the specified value and only one sample are allowed to be 70% lower than the specified value. 7.4 Packaging, Marking and Quality Certificate The packaging, marking and quality certificate shall conform to GB 247 and GB2101.

Appendix A Cross Reference for New and Old GB 700 Standard Designations (Only for Reference) A.1 The notation of designations and the technical requirements specified for the designations of GB700-88 are different from that of GB700-79, the following is cross reference for the new and old GB 700 standard designations: GB700-88 Q195

GB700-79

Irrespective of the grade, the chemical

#1

compositions

steel

and

mechanical

The chemical compositions of Q195 is

 properties (tensile strength, elongation

same as

and cold bending) shall be guaranteed.

(tensile strength, elongation and cold

However, the guaranteed mechanical

 bending) is same as

 properties can be otherwise spec ified in

for

related standards for rolled sheets and

conditions), there is no special steel in

 panels and strips according to the

#1 steel.

features

of

the

products

and

B1, the mechanical properties

Al

is

A1 (the tensile test

additional

guaranteed

the

requirements of use Q215 Q235

Grade A

A2

Grade B

C2

Grade A (without impact test, V-notch)

A3

(Additional guarantee, impact test at room temperature, V-notch)

Grade B

(with impact test at room

C3

o

temperature, V-notch)

Q255

room temperature-20 C, V-notch)

Grade C

(used as critical welding

--

Grade D

structure)

--

Grade A

A4

Grade B (with impact test at room

C4

temperature, V-notch) Q275

and

(Additional V-notch)

Irrespective of the grade, the chemical compositions

(Additional guarantee, impact test at

mechanical

 properties shall be guaranteed.

C5

guarantee,

impact

test,